What is bullet momentum as it applies to bullet weight? As in a very fast ultralight .357 Magnum round compared to a 230g +P .45 acp round with both of them generating 500 ft lbs. of energy. People will say the .45 round has more momentum. What exactly does that mean and how is it measured? (Assuming both bullets have similar construction and will not deform on impact). Buffalo Bore's website uses the example of a 50 grain .22-250 round zipping along at 3850 fps compared to a low-pressure 405 grain 45-70 round at 1350 fps with both developing a little over 1600 ft lbs of energy. That's a good picture and quite obvious but if the 22-250 bullet had an iron core and would not deform on impact why would the 45-70 have greater momentum and just exactly what does that mean?
I agree with their example but I can't define why I do nor can I get a solid explanation as to the why of the physics involved. If someone could steer me to a credible article explaining this I would greatly appreciate it.